Enhanced kill of sulfate reducing bacteria using timed sequential addition of oxyanion and biocide

ABSTRACT

A process is provided for the time dependent reduction and kill of cellular bacteria in a fluid by sequential exposure to nitrites and a low concentration of biocide. Oilfield water containing sulfate-reducing bacteria can be supplied with a timed sequential exposure of nitrite and biocide. The timed sequential addition of the biocide following exposure to the nitrite provides enhanced kill of the sulfate-reducing bacteria at concentrations of biocide that are lower than would be possible using simultaneous addition of these materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims benefit under 35 USC § 119(e) to U.S. Provisional Application Ser. No. 62/485,176 filed Apr. 13, 2017, entitled “ ENHANCED KILL OF SULFATE REDUCING BACTERIA USING TIMED SEQUENTIAL ADDITION OF OXYANION AND BIOCIDE,” which is incorporated herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

None.

FIELD OF THE INVENTION

The present invention relates generally to the control of biogenic sulfide production. More particularly, but not by way of limitation, embodiments of the present invention concern the use of at least one oxyanion and at least one biocide to synergistically inhibit sulfide production by sulfate-reducing bacteria.

BACKGROUND OF THE INVENTION

The presence of sulfides (e.g., H₂S, HS—, and S₂—) in fluids poses serious problems due to their toxicity, odor, and corrosive nature. It is well known that the presence of sulfides in many fluids is a consequence of the reduction of sulfates to sulfides by sulfate-reducing bacteria (SRB). SRB are routinely found in water associated with oil production systems and can be found in virtually all industrial aqueous processes including, for example, cooling-water systems, pulp and paper-making systems, chemical manufacturing, and petroleum refining.

It is also well known to use nitrite and biocide simultaneously to inhibit the activity of sulfate reducing bacteria (SRB). For many applications in the field, however, it would be preferred to completely eliminate or substantially reduce the number of sulfate reducing bacteria in the fluid, particularly in batch treatments.

BRIEF SUMMARY OF THE DISCLOSURE

The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the subject matter disclosed herein. This summary is not an exhaustive overview of the technology disclosed herein. It is not intended to identify key or critical elements of the disclosed subject matter or to delineate the scope of the disclosed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

The invention more particularly includes a method of killing sulfate-reducing bacteria in an aqueous medium by first contacting the sulfate-reducing bacteria with a first concentration of an oxyanion; and after contacting the sulfate-reducing bacteria with the first concentration of the oxyanion, contacting the sulfate-reducing bacteria with a second concentration of a biocide.

The oxyanion may be selected from the group consisting of nitrite, molybdate, tungstate, selenate, anthraquinone and combinations of one or more thereof.

The oxyanion is contacted with the sulfate-reducing bacteria for a specific time period which includes time periods between 2 hours and 2 weeks including 2 hours, 4 hours, 8 hours, 10 hours, 15 hours, 20 hours, 24 hours, 30 hours, 40 hours, 48 hours, 60 hours, 3 days, 4 days, 5 days, 1 week, 10 days, or 2 weeks.

In one embodiment, the biocide is not contacted with the sulfate-reducing bacteria until after completion of the specific time period.

The biocide may be selected from the group consisting of formaldehyde, glutaraldehyde, acrolein, quaternary amine compounds, cocodiamine, bronopol, 2-2-dibromo-3-nitrilo-propionamide (DBNPA), isothiazolone, carbamates, metronidazole, and combinations of one or more thereof.

In another embodiment, the oxyanion is a combination of more than one individual oxyanion and wherein the biocide is a combination of more than one individual biocide.

The oxyanion stresses the sulfate-reducing bacteria without directly killing the sulfate-reducing bacteria and the biocide directly kills the stressed sulfate-reducing bacteria. The aqueous medium may be oilfield water, a subterranean reservoir, and storage tank, pipeline, or other equipment that may be contaminated with sulfate-reducing bacteria.

While certain embodiments will be described in connection with the preferred illustrative embodiments shown herein, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings in which:

FIG. 1 shows the experimental results of a kill test measuring cellular ATP of SRB treated with two concentrations of nitrite and glutaraldehyde

DETAILED DESCRIPTION

Disclosed herein are various illustrative embodiments of a process for the time dependent reduction and kill of cellular bacteria in an aqueous medium by sequential exposure to oxyanions and a low concentration of biocide.

For example, oilfield water containing sulfate-reducing bacteria can be supplied with a timed sequential exposure of nitrite and biocide. The timed sequential addition of the biocide following exposure to the nitrite provides enhanced kill of the sulfate-reducing bacteria at concentrations of biocide that are substantially lower than would be possible using simultaneous addition of these materials.

In certain illustrative embodiments, a method of killing sulfate-reducing bacteria in oilfield water is provided. The sulfate-reducing bacteria can be contacted with a first concentration of an oxyanion selected from the group consisting of nitrite, molybdate, tungstate, selenate, anthraquinone and combinations of one or more thereof.

In one embodiment nitrite is prepared by mixing sodium nitrite (NaNO₂) with an aqueous solution. As low as 0.5 mM nitrite range, typically between 0.0003 and 1.5% NaNO₂ mass/volume (kg/m³) is prepared by mixing 3 to 750 g nitrite per L of solution. In one embodiment showed effective response with 200 mM (˜14 g/100 ml) Nitrite solution was prepared by mixing 13.8 g NaNO₂ with 100 ml brine solution.

The aqueous solution may be any solution suitable for use in a hydrocarbon reservoir including water, brine, salt water, reclaimed water, produced water, sea water, aquifer water, river water, and the like. In some embodiments the water may be pH balance, deoxygenated, filtered, treated to reduce dissolved solids, diluted and/or mixed with other solutions. In another embodiment deoxygenation is not required because the use of oxyanion followed by biocide reduces SRB in the reservoir. Further, oxyanion treatment followed by biocide may in some conditions allow use of produced water without significant treatment.

The biocide can be selected from the group consisting of formaldehyde, glutaraldehyde, acrolein, quaternary amine compounds, cocodiamine, bronopol, 2-2-dibromo-3-nitrilo-propionamide (DBNPA), isothiazolone, carbamates, metronidazole, and combinations of one or more thereof.

In one embodiment, glutaraldehyde (GA) is prepared fresh in concentrations from 0.01-1.8% depending upon activity required and reservoir conditions. In one embodiment a concentrated stock of 25% GA is diluted 1.872:100, in another embodiment 25% GA is diluted 2:100. Alternatively 50% GA may be diluted 1:100 to achieve a 0.5% GA solution. In yet another embodiment GA granules may be dissolved aqueous solution to a concentration of between 0.01 and 3% GA. The fresh GA solution should be used within a short period of time as the active GA concentration decreases over time.

The method provides contacting SRB in a reservoir with 0.0003% to 3% oxyanion for anywhere from two hours to two weeks. Contact time may be measured by providing a specified volume or percentage of the volume pumped for a period of time into the reservoir. Pump rates for chemical are likely to vary between 0.5 to 300 gallons/hour depending concentration and dosing. Treated injection water, 1000 barrels (bbls) of oilfield brine may be mixed. In one embodiment, 10 barrels (bbls) of oilfield brine may be mixed with 0.5 to 240 kg of sodium nitrate. The 10 barrels of nitrate solution are pumped at 1 barrel per minute until exhausted followed by a 10 barrels of 2% GA until exhausted. Nitrite and GA may be separated by a buffer solution or other barrier to prevent mixing before reaching reservoir depth. Once the GA reaches reservoir depth, the reservoir is shut in for 24 hrs or greater dependent upon well conditions and SRB levels.

In certain illustrative embodiments, the oxyanion can be a combination of more than one individual oxyanion and/or the biocide can be a combination of more than one individual biocide. Further, the oxyanion can comprise nitrite or consist essentially of nitrite, and the biocide can comprise glutaraldehyde or consist essentially of glutaraldehyde.

In certain illustrative embodiments, the oxyanion can stress the sulfate-reducing bacteria without directly killing the sulfate-reducing bacteria, thus allowing the biocide to directly kill the sulfate-reducing bacteria. Because the bacterial cell is dead following the treatment, continuous exposure of the chemicals is not required to control further activity. Also, the pre-exposure to the oxyanion stresses the bacterial cell which allows for much lower cidal doses of biocide to be used.

The following examples of certain embodiments of the disclosed subject matter are given. Each example is provided by way of explanation of the disclosed subject matter, one of many embodiments of the disclosed subject matter, and the following examples should not be read to limit, or define, the scope of the disclosed subject matter.

Test 1

An initial test was performed to examine the effects of nitrite on cellular adenosine triphosphate (cATP) response in a Barnett sulfate reducing bacteria (SRB) culture. Standard SRB bottles (1% NaCl) were utilized. Sterile pipets, and not syringes, were used to add chemicals and inocula. Serial dilutions were done with syringes. Serial dilutions were performed outside of the anaerobic chamber, but otherwise, the steps were performed inside a glove box using an aseptic technique.

Synthetic brine was the kill medium. Sterile, anaerobic, phosphate buffered saline containing 1% NaCL (500 mL) and glutaraldehdye stock (25% Sigma Aldrich) prepared the day of test were utilized. A 0.5% GA (w/v) solution was prepared. 1.872 mL of GA stock (25%) was added to 100 mL of synthetic brine above, and pH was recorded. For the 200 mM NaNO₂ solution, 13.8 g NaNO₂ were added per 100 mL of synthetic brine above.

The procedure for the kill test was as follows: (Step 1) Pool all the positive SRB bottles (minus any nails) into a sterile, anaerobic, serum bottle inside glove box (maximum of 110 mL of inocula). Cap, but do not seal the serum bottle; (Step 2) Measure cATP level in the inoculum and report microbial equivalents (ME) per mL. Should use less than 5 mL of inoculum; (Step 3) Measure sulfide level in inoculum and report in mg/L. Should use less than 5 mL of inoculum; (Step 4) Label 4×50 mL, sterile, anaerobic serum bottles as follows: #1 Control (no biocide); #2 Nitrite; #3 12.5 ppm GA; #4 12.5 ppm GA+nitrite; (Step 5) Add 10 mL of synthetic brine to each of the 4 test bottles in Step 4; (Step 6) Add 10 mL of inocula to each of the 4 test bottles in Step 4; (Step 7) Add 0.1 mL of NaNO₂ solution to bottle #2; Add 0.05 mL of 0.5% GA solution to bottle #3; Add 0.05 mL of 0.5% GA solution+0.1 mL of NaNO₂ solution to bottle #4; Incubate all bottles at 30° C. for 2 hours; (Step 8) Shoot a series of 8 SRB bottles (serial tenfold dilutions) for each test bottle in Step No. 6 above. Incubate these bottles at 30° C.; (Step 9) Incubate the remaining bottles at 30° C. for another 22 hours; (Step 10) Repeat Step 7.

The procedure for the nitrite/cATP test was as follows: (Step 1) Label 3×50 mL, sterile, anaerobic serum bottles as follows: #1 Control (no nitrite); #2 NitriteA; #3 NitriteB; (Step 2) Add 20 mL of synthetic brine to each of the 3 test bottles in Step 1; (Step 3) Add 20 mL of inocula to each of the 3 test bottles in Step 1; (Step 4) Add 0.2 mL of NaNO₂ solution to bottle #2 and 0.4 mL of NaNO₂ solution to bottle #3; (Step 5) Cap and incubate at 30° C. (keep in glove box); and (Step 6) At times 0, 2 h, 4 h, and 24 h run cATP on both control and nitrite samples. The cATP test can be conducted outside the glove box.

The experimental results in FIG. 1 demonstrate that pretreating with oxyanion prior to biocide treatment is more effective than nitrite treatment, biocide treatment, or simultaneous nitrite and biocide treatment.

Test 2

A follow-up test was performed. Similar preparatory steps were performed as in Test 1. Synthetic brine was the kill medium, specifically, a sterile, anaerobic, phosphate buffered saline containing 1% NaCl (500 mL). Glutaraldehdye Stock (25% Sigma Aldrich) was prepared the day of test. 0.5% GA (w/v) solution was prepared by adding 1.872 mL of GA stock (25%) to 100 mL of synthetic brine above. pH was recorded. For the 200 mM NaNO₂ solution, 13.8 g of NaNO₂ was added per 100 mL of synthetic brine above.

The procedure for the kill test was as follows: (Step 1) Pool all the positive SRB bottles (minus any nails) into a sterile, anaerobic, serum bottle inside glove box. (maximum of 100 mL of inocula); Cap, but do not seal the serum bottle; (Step 2) Measure cATP level in the inoculum and report microbial equivalents (ME) per mL; use less than 5 mL of inoculum; (Step 3) Measure sulfide level in inoculum and report in mg/L; use less than 5 mL of inoculum; (Step 4) Label 4×50 mL, sterile, anaerobic serum bottles as follows: #1 Control (no biocide); #2 Nitrite; #3 20 ppm GA; #4 20 ppm GA+nitrite; (Step 5) Label another 4×50 mL, sterile anaerobic serum bottles as follows: #5 Control-delayed; #6 Nitrite—delayed; #7 20 ppm GA—delayed; #8 20 ppm GA+nitrite—delayed; (Step 6) Add 10 mL of synthetic brine to each of the 4 test bottles in Step 4, and the 4 bottles in Step 5; (Step 7) Add 10 mL of inocula to each of the 4 test bottles in Step 4, and the 4 bottles in Step 5; (Step 8) Add 0.2 mL of NaNO₂ solution to bottle #2, add 0.08 mL of 0.5% GA solution to bottle #3, add 0.08 mL of 0.5% GA solution+0.2 mL of NaNO₂ solution to bottle #4, incubate all bottles at 30° C. for 2 hours and shoot a series of 8 SRB bottles (serial tenfold dilutions) for each of the 4 test bottles in Step 4 above and incubate at 30° C.; (Step 9) Add 0.2 mL of NaNO₂ solution to bottle #6 and bottle #8 ONLY (see Step 5), incubate all bottles at 30° C. for 24 hours in chamber, add 0.08 mL of 0.5% GA solution to bottle #7 and bottle #8 ONLY; then measure cATP levels in bottles #5 and #6 only, Incubate all 4 bottles for 2 hours after adding GA to bottles #7 and #8, and shoot a series of 8 SRB bottles (serial tenfold dilutions) for each of the 4 test bottles in Step 5 above and incubate at 30° C.

The results from these follow-up tests are provided in Table 1: Experimental Results of Planktonic Kill Study as number of positive bottles using serial dilution method as a number of positive bottles growth.

Nitrite No Delay 24 hrs (cells/mL) (cell/mL) Control 1.0E+08 1.0E+08 200 μL Nitrite 1.0E+08 1.0E+08 200 ppm GA 1.0E+07 1.0E+06 GA + NO₂ 1.0E+06 0

The experimental results in Table 2 demonstrate that 200 mM nitrite decreased the cellular tolerance for glutaraldehyde and provided a synergistic kill effect to prevent growth under cultivation conditions.

These tests demonstrate that sequential treatment with oxyanion followed by biocide are much more effective the biocide treatment alone, oxyanion treatment alone, and simultaneous treatment with biocide and oxyanion treatment. Recommended treatment for the removal or prevention of SRB in a hydrocarbon reservoir involve pumping an oxyanion solution into the reservoir for a first treatment period followed by pumping of a biocide solution into the reservoir for a second treatment period. Because the treatment flows through the tubing, pipes, and equipment—the treatment can be used to remove SRB contamination from all equipment it is exposed to including the reservoir, storage tanks, pumps, pipes, and the like.

While several embodiments have been provided in the present disclosure, it may be understood that the disclosed embodiments might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or process or certain features may be omitted, or not implemented.

In addition, the various embodiments described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and may be made without departing from the spirit and scope disclosed herein.

In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. At the same time, each and every claim below is hereby incorporated into this detailed description or specification as additional embodiments of the present invention.

Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims while the description and abstract are not to be used to limit the scope of the invention. The invention is specifically intended to be as broad as the claims below and their equivalents.

REFERENCES

All of the references cited herein are expressly incorporated by reference. The discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication data after the priority date of this application. Incorporated references are listed again here for convenience:

1. “Inhibition of biogenic sulfide production via biocide and metabolic inhibitor combination,” U.S. Pat. No. 7,833,551, issued Nov. 16, 2010.

2. “Inhibition of biogenic sulfide production via biocide and metabolic inhibitor combination,” U.S. Pat. No. 8,846,732, issued Sep. 30, 2014. 

1. A method of killing sulfate-reducing bacteria in an aqueous medium, the method comprising the steps of: contacting the sulfate-reducing bacteria with a first concentration of an oxyanion; waiting a specific time period; and contacting the sulfate-reducing bacteria with a second concentration of a biocide.
 2. The method of claim 1, wherein the oxyanion is selected from the group consisting of nitrite, molybdate, tungstate, selenate, anthraquinone and combinations of one or more thereof.
 3. The method of claim 1, wherein the specific time period comprises between 2 hours and 2 weeks including 2 hours, 4 hours, 8 hours, 10 hours, 15 hours, 20 hours, 24 hours, 30 hours, 40 hours, 48 hours, 60 hours, 3 days, 4 days, 5 days, 1 week, 10 days, or 2 weeks.
 4. The method of claim 1, wherein the biocide is selected from the group consisting of formaldehyde, glutaraldehyde, acrolein, quaternary amine compounds, cocodiamine, bronopol, 2-2-dibromo-3-nitrilo-propionamide (DBNPA), isothiazolone, carbamates, metronidazole, and combinations of one or more thereof.
 5. The method of claim 1, wherein the oxyanion is a combination of more than one individual oxyanion and wherein the biocide is a combination of more than one individual biocide.
 6. The method of claim 1, wherein the oxyanion comprises nitrite.
 7. The method of claim 1, wherein the oxyanion consists essentially of nitrite.
 8. The method of claim 1, wherein the oxyanion stresses the sulfate-reducing bacteria without directly killing the sulfate-reducing bacteria and the biocide directly kills the sulfate-reducing bacteria.
 9. The method of claim 1, wherein the aqueous medium is oilfield water. 